Polymers having functional end groups are well-known and are useful as starting materials for adhesives, coating materials, sealants, etc. Examples of such polymers include polyalkylene oxides having hydroxyl groups on both ends of the polymer chain, which are referred to as telechelic polymers, used to prepare polyurethanes.
Isobutylene polymers having functional end groups can be produced by the INIFER process, in which isobutylene is cationically polymerized using a halogenated compound, such as 1,4-bis(.alpha.-chloroisopropyl) benzene (hereinafter referred to as p-DCC), as an initiator and chain transfer agent and a Lewis acid such as BCl.sub.3, as a catalyst. That process is described in U.S. Pat. No. 4,276,394 specification of which is incorporated therein by reference.
Isobutylene polymers having chlorine atoms at both ends of the polymer chain obtained by the INIFER process can easily be converted by dehydrochlorination into a polymer having isopropenyl groups at both ends. The polymer having isopropenyl groups can be readily converted by hydroboration to polymers having hydroxyl groups bonded to the primary carbon at each end of the polymer chain.
However, in the polymerization of isobutylene by the INIFER process, as described above, there is a problem that side-reactions tend to occur and considerable amounts of polymers having various kinds of end groups (such as ##STR2## (indanyl group),etc.) are produced, in addition to the desired chlorine-containing ( C(CH.sub.3).sub.2 Cl) end group. These side reaction can occur under very mild conditions, even when the polymerization temperature is as low as from -50.degree. to -70.degree. C., and the monomer concentration is as dilute as about 1M.